title: Analgesic effect of a mixed T-type channel inhibitor/CB2 receptor agonist.
abstract: BACKGROUND
  Cannabinoid receptors and T-type calcium channels are potential targets for treating pain. Here we report on the design, synthesis and analgesic properties of a new mixed cannabinoid/T-type channel ligand, NMP-181.
  
  
  RESULTS
  NMP-181 action on CB1 and CB2 receptors was characterized in radioligand binding and in vitro GTPγ[35S] functional assays, and block of transiently expressed human Cav3.2 T-type channels by NMP-181 was analyzed by patch clamp. The analgesic effects and in vivo mechanism of action of NMP-181 delivered spinally or systemically were analyzed in formalin and CFA mouse models of pain. NMP-181 inhibited peak CaV3.2 currents with IC50 values in the low micromolar range and acted as a CB2 agonist. Inactivated state dependence further augmented the inhibitory action of NMP-181. NMP-181 produced a dose-dependent antinociceptive effect when administered either spinally or systemically in both phases of the formalin test. Both i.t. and i.p. treatment of mice with NMP-181 reversed the mechanical hyperalgesia induced by CFA injection. NMP-181 showed no antinocieptive effect in CaV3.2 null mice. The antinociceptive effect of intrathecally delivered NMP-181 in the formalin test was reversed by i.t. treatment of mice with AM-630 (CB2 antagonist). In contrast, the NMP-181-induced antinociception was not affected by treatment of mice with AM-281 (CB1 antagonist).
  
  
  CONCLUSIONS
  Our work shows that both T-type channels as well as CB2 receptors play a role in the antinociceptive action of NMP-181, and also provides a novel avenue for suppressing chronic pain through novel mixed T-type/cannabinoid receptor ligands.
authors.affiliation: Department of Physiology and Pharmacology, Hotchkiss Brain Institute, University of Calgary, Calgary, Canada.
authors.forename: Vinicius M
authors.initials: VM
authors.lastname: Gadotti
authors.forename: Haitao
authors.initials: H
authors.lastname: You
authors.forename: Ravil R
authors.initials: RR
authors.lastname: Petrov
authors.forename: N Daniel
authors.initials: ND
authors.lastname: Berger
authors.forename: Philippe
authors.initials: P
authors.lastname: Diaz
authors.forename: Gerald W
authors.initials: GW
authors.lastname: Zamponi
mesh_terms: D000700:Analgesics / Q000737:chemistry / Q000494:pharmacology*; D000818:Animals; D016466:CHO Cells; D020747:Calcium Channels, T-Type / Q000235:genetics / Q000378:metabolism*; D002227:Carbazoles / Q000737:chemistry / Q000494:pharmacology*; D003412:Cricetulus; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009025:Morpholines; D010147:Pain Measurement; D011720:Pyrazoles; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists* / Q000378:metabolism
chemical_list: D000700:Analgesics; C479952:CACNA1H protein, human; C469757:CACNA1I protein, human; D020747:Calcium Channels, T-Type; D002227:Carbazoles; D009025:Morpholines; C586525:NMP-181; D011720:Pyrazoles; D043885:Receptor, Cannabinoid, CB2; C109925:AM 281